I. Field of the Invention
The present invention relates to the field of laminoplasty, and, more particularly, to laminoplasty devices and methods.
II. Discussion of the Prior Art
Spinal stenosis is a degenerative narrowing of the spinal canal, nerve root canals and/or intervertebral foramina caused by bone and/or ligament hypertrophy in local, segmental or generalized regions. The narrowing results in compression of spinal nerves and nerve roots, causing a constellation of symptoms, including neck or lower back pain, neurogenic claudication and extremity pain. The leading cause of spinal stenosis is normal wear and tear on the spine, occurring in virtually the entire adult population during the natural process of aging, although spinal stenosis can occur at any age due to trauma, disease, or some medical conditions.
Surgery is currently the only treatment designed and proven to provide long term relief from spinal stenosis. One way of relieving spinal cord pressure is a surgical procedure called a laminoplasty. Laminoplasty is a surgical procedure for treating spinal stenosis (and other conditions) by relieving pressure on the spinal cord. The traditional “open door” laminoplasty procedure involves making cuts in the lamina on both sides of the spinous process of the affected vertebrae (i.e. cutting completely through the lamina on one side of the spinous process and cutting partially through the lamina on the other side of the spinous process) and then swinging the freed flap of bone open to relieve pressure on the spinal cord. For this “open door” laminoplasty procedure, one challenge is to securely maintain the grooved portion of lamina or “lamina hinge portion” for proper healing. Because the hinged side can be prone to breakage if excess pressure is applied on the lamina, the open side gutter is generally cut first, followed by the hinge side. A curved curette or nerve hook can be used to test the stability of the hinge to ensure that sufficient opening can be achieved. A graft and/or plate can then be inserted into the created opening to keep the lamina in an open position.
The existing standard open door laminoplasty technique is comprised of several steps. First, a complete cut of the lamina (called a “trough cut”) is made on one side of the spinous process at the base of the lamina, where it meets the lateral mass. The bone is resected through the dorsal cortex, inner cancellous layer and ventral cortex. After this, a partial cut (called a “hinge cut”) is performed on the opposite side of the spinous process, resecting the lamina where the lamina meets the lateral mass; only the dorsal cortex and inner cancellous layers are removed. A plate is then placed on the trough side spanning a gap between the severed lamina and the lateral mass, and the lateral mass screws are inserted through one end of the plate and into the lateral mass. Finally, the laminar screw is inserted through the other end of the plate and into the lamina.
This traditional procedure can be risky to perform largely because the cuts in the lamina are made before the hole for the laminar screw are drilled. This means that the surgeon is likely drilling through an unstable lamina directly over otherwise exposed spinal cord. The present invention is directed at overcoming, or at least improving upon, the disadvantages of the prior art.